The development of inverting generators, because of its small size, light weight, good electrical properties and many other advantages, has progressed rapidly in recent years in the field of small engine generators. The working principle of existing inverting generators is as follows: A multi-pole AC permanent-magnet generator is used for generating an equiamplitude alternating current of higher frequency, which is rectified into a constant direct current through a controllable rectifying method and then converted into the desired alternating current through an inverting circuit, which is commonly known as the ADA way.
An existing ADA inverting circuit chops the direct current through a bridge circuit and an IGBT power transistor, and then the waveform is shaped through an LC circuit, so as to restore it into an AC sine wave. Because a greater switching loss may be caused due to the use of the IGBT power transistor working at the chopping frequency of 20 K, the transistor generates heat and suffers from power loss and reduced efficiency. Meanwhile, the high-power inductor used for shaping the chopped waveform also generates much heat and thus results in a great loss. At the same time the multiple harmonics having the chopping frequency of 20 K may generate a high-frequency electromagnetic wave. If the power of the generator is to be increased, the electromagnetic wave will also be increased, which will be unable to meet the existing European EMC certification requirements.
In the prior art, the alternating current close to the sine waveform can also be obtained by rectifying the equiamplitude alternating current of higher frequency directly with the controllable rectifying method and meanwhile controlling the conduction angle at different times. However, the waveform has a greater degree of distortion, which will change more greatly under different loads, and thus the requirements of many electric appliances cannot be met.
From a cost perspective, prices of the IGBT high-power transistor, the high-capacity electrolytic capacitor, and the high-power inductor used in the ADA inverting mode tend to be high, and the specification of the IGBT transistor increases with the current, with the price increasing exponentially, and thus the cost will be higher for the manufacture of a generator having a power of 5 kW or greater. Therefore, currently it is difficult to replace traditional generators with inverting generators.